Validate that typegen script can run in action (#51189)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/51189

Changelog: [Internal]

Adds a Github action that validates that the typegen script can successfully translate every necessary Flow file to TypeScript.

Reviewed By: huntie

Differential Revision: D74390916

fbshipit-source-id: 8c6d554c8681a2b92a8b182244a329ee538d9e53